Little portable generators

[2WheelsNot4]

I was wondering if anyone has the specs offhand for what type of power a standard 4A charger is ? I know its 240v, but i think wattage or ampage is the important bit(Sorry,utterly clueless about most things electrical.)

Was wondering if I were to go away on a car camping trip, which for me is usually the Highlands of Scotland, miles and miles from the nearest habitation, how would I recharge the bike if i brought an ebike instead of a non ebike.
I've not the money for a big Honda or Yamaha generator, but Clarke for example do 800w and 1200w for roundabout £300. But would either of those be suitable to recharge the battery.

Anyone tried or went this route ?.

 

[Mteam]

Either of those generators will run an ebike charger, you just need to make sure you have enough fuel to run for however long it takes to charge.

I've got one of the 800w generators ( but not not for charging ebikes), they work fine,but they are quite noisy, so you might annoy people by running them for several hours

 

[flash]

Volts x Amps = Watts.

240 x 4 = 960.

Although you probably wont need that much as your charger is probably variable voltage. (110 x 4 = 440) I've charged bikes off a 600W inverter with no issues. But I haven't experimented to see what the smallest system is that'll work with my charger. My reverse maths says around 300W would be enough (based on battery capacity/charging time required and working backwards). I'd still go for 600w.

That's a noisy 4-5 hours though. Personally I'd spend extra to get a leisure battery and inverter.

 

[2WheelsNot4]

I know theyre noisy, but we usually camp alone, nowhere near anyone and rarely in a site, so noise wouldnt for the most part be a problem.
But thanks for the info. Probably best with the 1200w.

But maybe retrofit a small motorbike muffler might reduce to noise output
Actually when i was in the scouts yonks ago we had a small generator which had a box that went over the top which had thick padding on the inside. I guess that there was still air intake, but the concept does make sense. I'll take a look now to see if any YT vids on quietening down these things, should the need for a site camp ever arise

 

[dobbyhasfriends]

The Honda ones are really quiet but are the same cost as a leisure battery setup.. and then you don't have to take petrol everywhere either

 

[urastus]

I was wondering if anyone has the specs offhand for what type of power a standard 4A charger is ? I know its 240v, but i think wattage or ampage is the important bit(Sorry,utterly clueless about most things electrical.)

Was wondering if I were to go away on a car camping trip, which for me is usually the Highlands of Scotland, miles and miles from the nearest habitation, how would I recharge the bike if i brought an ebike instead of a non ebike.
I've not the money for a big Honda or Yamaha generator, but Clarke for example do 800w and 1200w for roundabout £300. But would either of those be suitable to recharge the battery.

Anyone tried or went this route ?.

I've just bought a generator. You kind of need a generator with double the output capacity of what you need, otherwise the motor will be running at maximum capacity and it will be loud. It probably won't last long that way either and use a lot of fuel. We bought one to charge a power station on longer trips away. The plan is to charge the ebike from the power station (as well as run a small fridge etc). We'd probably run it for just an hour now and then when not many folk are around (wherever we're camping); that's the beauty of having a reasonably sized power station (2000Wh).

In Aus Gentrax have a great reputation for being cheap, quiet and reliable. I think King's generators are rebranded gentrax (in Aus)

 

[Slapbassmunky]

The smaller 800W generators make a hell of a noise. I use a slightly bigger Clarke 1200W generator, because of it's bigger engine it's much more 'relaxed' and far less annoying. It'll happily charge 4 bikes without breaking a sweat (no doubt it would charge more) and uses very little fuel. I was initially worried about it being too noisy, but by the time everyone's hit the car park for lunch, the dubstep and weed smoke drowns it out nicely

 

[Stoffel]

Ebikes charged by petrol, I love it!

Please tweet Greta Thunberg a video of it charging

 

[Slapbassmunky]

Ebikes charged by petrol, I love it!

Please tweet Greta Thunberg a video of it charging

The comments from the guys riding to the uplift wagon were fantastic. Pointing out to them that a big diesel transit van was taking them to the top seemed to go over their heads

 

[Stoffel]

The comments from the guys riding to the uplift wagon were fantastic. Pointing out to them that a big diesel transit van was taking them to the top seemed to go over their heads

My dream is to drive a Tesla through the London low emission zone towing a diesel generator which is charging the battery

 

[Keggie]

Must be an inverter generator or you might kill the electronics within the charger and battery ,
I bought a champion mighty atom about £500

 

[Planemo]

I use a slightly bigger Clarke 1200W generator, because of it's bigger engine it's much more 'relaxed' and far less annoying. It'll happily charge 4 bikes without breaking a sweat (no doubt it would charge more)

I'm not saying it's not working as it clearly is. But I think my math may be skewed as I thought 4A/240v would use around 960w. So for 3 bikes it should need a lot more than 1200w.

 

[Mteam]

I'm not saying it's not working as it clearly is. But I think my math may be skewed as I thought 4A/240v would use around 960w. So for 3 bikes it should need a lot more than 1200w.

most likely explanation could be because a 4amp charger probably doesnt draw a continuous 4amps? I dunno - but obviously it works.

 

[Planemo]

most likely explanation could be because a 4amp charger probably doesnt draw a continuous 4amps? I dunno - but obviously it works.

The only time a 4A charger doesn't draw 4A is right at the end of the cycle when peak voltage is neared and balancing starts to occur on the constant voltage phase as the current phase drops.

As I say, maybe my math is wrong, the generator chucks out more than its rated for or the chargers are not actually giving the full 4A but are still managing to work to some extent.

 

[Slapbassmunky]

I'm not saying it's not working as it clearly is. But I think my math may be skewed as I thought 4A/240v would use around 960w. So for 3 bikes it should need a lot more than 1200w.

So you think a 4A Bosch charger is pulling almost a kilowatt from the mains supply?

Yeah dude, your maths is way off.....

4A @ 42v peak before balancing means the charger is supplying 164W maximum to the battery. If the charger is 90% efficient (which it will be) then you're pulling roughly 200W peak, per 4A charger. It dosen't quite pan out like this because the power factor of a switch mode charger/power supply is crap. But suffice to say 4 X 4A Bosch chargers off that generator is fine.

 

[Slapbassmunky]

The only time a 4A charger doesn't draw 4A is right at the end of the cycle when peak voltage is neared and balancing starts to occur on the constant voltage phase as the current phase drops.

A 4A charger PROVIDES 4A continuous when in CC mode before balancing and current tapering.

Provided watts to the battery actually increase with charge capacity, because the charger provides a constant current and the battery voltage increases from 30v to 42v - 120W to 164W

 

[Planemo]

Yeah dude, your maths is way off.....

Yep! Brain fade. I was working on 4A at 240v...not 42v... I did think something was amiss...

But as an aside to your later post, the charger should output a constant current up until near saturation. Thats why it's called 'constant current' phase. It matters not what the battery voltage is up until that point. Only after that point does 'constant voltage' phase take over and current reduces.

Below is a graph I did on my unicycle. It's a 6A charger and a 100.8v system but the process is the same. Blue line is voltage, red is current.

 

[Slapbassmunky]

Yep! Brain fade. I was working on 4A at 240v...not 42v... I did think something was amiss...

But as an aside to your later post, the charger should output a constant current up until near saturation. Thats why it's called 'constant current' phase. It matters not what the battery voltage is up until that point. Only after that point does 'constant voltage' phase take over and current reduces.

Below is a graph I did on my unicycle. It's a 6A charger and a 100.8v system but the process is the same. Blue line is voltage, red is current.

View attachment 85430

Yeah I know, I oversimplified the explanation and edited accordingly. Yes lipo uses a standard cc-cv charge profile, just like a basic lead acid charger. Handy when you want to use a power supply or LED driver as a charger

 

[Slapbassmunky]

Below is a graph I did on my unicycle. It's a 6A charger and a 100.8v system but the process is the same. Blue line is voltage, red is current.

View attachment 85430

If I'm reading that right the charger took over two hours in CV mode. Is that a well used pack as I'd say the internal resistance is getting a bit high?

 

[Planemo]

I must admit it was charged a bit longer than I usually would as it was for testing purposes. Bear in mind the time that the green light on the charger came on (around an hour previous). I wanted to run it until current had dropped down to a point where it wasn't falling any longer, thereby meaning totally saturated and fully balanced. But yes it's quite long, partly because it was a big pack (1860Wh 20P) and also because it hadn't had a balance charge for about 3 cycles, so the cells were further out of balance than they would normally be, thus needing more time to balance.

As an aside, this testing (there was more) proved beyond doubt that partial charging is not good at all. Occasionally I have to if I am out all day, sometimes I have partial charged 3 times in one day. But it's not ideal by any stretch and does mean that the next full charge will take longer. People don't realise how quickly cells can fall out of balance! The pack itself was in good order BTW.

 

[Slapbassmunky]

I must admit it was charged a bit longer than I usually would as it was for testing purposes. Bear in mind the time that the green light on the charger came on (around an hour previous). I wanted to run it until current had dropped down to a point where it wasn't falling any longer, thereby meaning totally saturated and fully balanced. But yes it's quite long, partly because it was a big pack (1860Wh 20P) and also because it hadn't had a balance charge for about 3 cycles, so the cells were further out of balance than they would normally be, thus needing more time to balance.

As an aside, this testing (there was more) proved beyond doubt that partial charging is not good at all. Occasionally I have to if I am out all day, sometimes I have partial charged 3 times in one day. But it's not ideal by any stretch and does mean that the next full charge will take longer. People don't realise how quickly cells can fall out of balance! The pack itself was in good order BTW.

A smart BMS set to 3.7v static balance. That'll solve your minor issue. I've found the difference between charging to 4.1. Vs 4.2v per cell when you can greatly increases pack longevity. Most big brand e-bike batteries don't just top balance but start the job at a much lower threshold, then work away until the pack 'sleeps'. Anyway, I digress. Generators!......